Method for the production of hydraulic lime and cement from combustion residues of sewage, canal-sludge, or the like.



i it] JULIUS ELSNER, 0F BERLIN-FRIEDENAU, GERMANY.

METHOD FOR THE PRODUCTION OF HYDRAULIC LIME AND CEMENT FROM COMBUSTIONRESIDUES OF SEWAGE, CANAL-SLUDGE, OR THE LIKE.

Patented Mar. 27, 19117.

No Drawing. Application filed December 26, 1913, Serial No. 808,920.Renewed January 29, 1917. Serial No. 145,2805.

To all whom it may concern:

Be it known that I, JULIUS ELSNER, engineer, subject of -the GermanEmperor, residing at Kaiser Allee 74, Berlin-Friedenau, Germany, haveinvented a certain new and useful Improved Method for the Production ofHydraulic Lime and Cement from Combustion Residues of Sewage,CanaLSIudge, or the like; and I hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

In the combustion and the removal of gases from wastes such as sewage,canal sludge and the likethe residues amount to about one half of thetotal of the treated material so that the economical qualities ofcombustion apparatus of this kind are essentially submitted to theutilization of the said residues.

According to this invention these residues are treated to give hydrauliclime, ordinary cement or Portland cement in a more simple manner thanhitherto, that is without making use of more expensive processes, theabove products being obtained according to the nature of the residuesand the quantity and kind of the additional substances.

In carrying out this invention the residues, according to theircomposition, are treated with lime and other additional substances andsubsequently a contact salt is added such as chlorid of calcium,aluminium and magnesium salts. The mixture is then subjected to a heatvarying from 650 to 1050 degrees centigrade Without however causingmelting. It is advantageous for the expedition of the reaction to carryout the latter in an atmosphere of steam and air.

1 The sewage-oven residues consist of approximately 53 per cent. SiO 12per cent. A1 0 11 per cent. Fe O 15 per cent. CaO, 1.5 per cent. MgO, 2per cent. sulfur and phosphorus and -5.5 per cent. alkali metalchlorids. If for example such a residue has added to it 1.39 times itsweight of lime and a proportional amount of contact salt and if thewhole is subjected to a heat of from 600 to 1050 degrees Centigradeduring a short time an excellent Portland cement can be obtainedcomprising about 65 per cent. CaO,

23 per cent. E50,, 5 per cent. A1 0,, 4.6 per cent. Fe O which is a goodaverage of the composition of Portland cement. The kind and quality ofthe additional substances are determined by the composition of the rawmaterials and the kind of the desired final product.

When the gases are to be removed from sludge the additional substancesmay be added before said removal takes place, whereby the removal ofgases, which is carried out in a temperature of from 400 to 700 degreescentigrade, is united with the hereinbefore described process. 1

In strongly ferruginous residues the content of iron is diminished bysuitable means preferably before the mixture is subjected to thechemical reaction in the furnace. The iron can be removed in any desiredmanner or its proportion is reduced by an increased addition of lime,clay, silica and so forth. The additional substances, calcium oxid,lime-stone, silicates, blast furnace slag or the like can be added tothe raw material before the combustion takes place in the sewage-oven.By mixing residues poor in lime and rich in iron with blast furnace slagrich in lime and poor in iron great advantages may be cbtained in suchdistricts where suitable blast furnace slag is cheap. The addition oflime and consequently that of contact salts are hereby reduced so thatthe costs of production are minimized.

To disintegrate and also to comminute the residues discharged fromthesewage combustion oven or from the sewage gas distillation apparatussaid residues are exposed -to a current of a1r, or of steam, or of a mu-'ture of steam and air.

This process is however not intended to form part of the presentinvention.

The contact salts may be either in liquid or in pulverized or incrystallized form and can be mixed with the residues either before orafter their grinding.

Having now fully described my invention and the manner in which it is tobe carried out, I declare, that what I claim, is:

Method for the production of cement, from a combustion residue of sewagecontaining about 53% silica, about 23% total of oxids of iron andaluminium, about 15% of calcium oxid, and about 5% of alkali metalchlorids, consisting in mix ng such residue with at least substantiallyan equal amount my invention I have signed my name in 01f lime, and withcalcium ch%orid, heating presence of two subscribing witnesses. t 1emixture to a temperature 0 600 to 1050 centigrade for a sufficient timeto form a JULIUS ELSNER' 5 Portland cement and treating the mixtureWitnesses:

with steam and air during said heating. HENRY HASPER,

In testimony that I claim the foregoing as WOLDEMAR HAUPT.

